This invention relates generally to a computer automated system and method for converting a hard copy source document bearing alphanumeric text and symbols relating to the physical dimensions and edges of a three dimensional object and of symbol properties of the symbol used in association with the three dimensional object into a drawing file consisting of three dimensional coordinates and vectors and corresponding to the physical dimensions and edges of the object and to the symbol properties of the symbol, and in particular, to a computer automated system and method for converting engineering drawings and architectural plans. The invention is particularly well-suited for utilizing and converting a raster image of a scanned source document bearing a drawing view, symbols and alphanumeric text relating to heights, widths, depths (lengths), and angles of edges of the three dimensional object and of the symbols into mathematically accurate vector computer drawing files based on the symbols and alphanumeric text scanned from the source document. The invention is also well suited for utilizing a raster image produced by scanning an engineering drawing document having a having at least one view thereon showing the edges of a three dimensional object and having alphanumeric text relating to the lengths and directions of lines and curves corresponding to the edges of the object, where the invention constructs a mathematically accurate drawing of the view from the raster file. The present invention is also well-suited for scanning a hard copy architectural plan bearing symbols and alphanumeric text relating to the size, shape, location and elevation of various structural components, such as, but not limited to, walls, windows, and doors and converting the symbols and alphanumeric text into a mathematically accurate computer drawing of the architectural plan.
With the development of various interactive Computer Aided Drafting (also often referred to as Computer Aided Design) (hereinafter, CAD) software, architects, engineers, their draftspersons, and/or technicians (collectively, hereinafter "users") are able to produce architectural plans and engineering drawings using computer drawing files more easily, quickly and accurately than using traditional hand drafting techniques. Besides the ease, speed and accuracy of producing these plans and drawings, the resultant computer drawing files are easier to edit and alter to create new drawings and plans. They are easier to store; they are easier to share with other technicians; and the drawing files can be exported to other computer applications. In the case of architectural plans/drawings, for example, the finished drawings can be rendered in different views, materials lists can be generated, loads can be calculated and structural members can be tested for integrity. In the case of engineering drawings, for example, structural calculations can be made testing the integrity of design elements and the drawing can be exported to a Computer Aided Manufacturing (CAM) environment. In the CAM environment, exact instructions from the computer program related to the dimensions of an object can be fed to an external manufacturing machinery which in turn produces the object ported in the drawing file. The overall advantages of being able to rapidly test and alter designs is well known in the art.
Revising the CAD drawings is easier and more accurate than revising hand drafted drawings. In CAD, the lines on the drawings are represented as vectors. CAD vectors can be manipulated electronically. With the click of a mouse button, lines can be copied, erased, bisected, offset or rotated. The same operations in a hand drawing environment would involve the use of several tools such as erasers, pencils, protractors, scaling rulers and straight edges. But, what makes CAD qualitatively different from hand drawing, is that the vectors representing the lines in the drawing are actually mathematical expressions and not mere representations of the dimensions of the lines. Therefore, any CAD operation performed on an accurately constructed vector would produce mathematically meaningful results. Complex geometric functions can be performed by manipulating vector entities.
Unfortunately, CAD use is relatively new, having become a significant drafting modality in the past 15 years. Even today, only about 50% of the architectural plans and engineering drawings are being produced in this manner. It is estimated that about 80% of drawings and plans exist in the form of hard copy paper documents.
One of the major tasks facing industry, business and government is organization and storage of architectural and engineering information for further utilization. Currently, much of the information is stored in the form of hand drawn hard copy source documents, e.g., mechanical drawings, such as, engineering drawings and architectural plans/drawings, having various formats and scales. These documents, which are commonly drawn on paper, typically contain a scaled hand drawing of various views and components of the three dimensional (3D) object. As used hereinthroughout, the term "3D" means three dimensional; and the term "2D" means two dimensional. The 3D object may be, but is not limited to, an article of manufacture as drawn in an engineering drawing, or to a structure as drawn in an architectural drawing. As is known in the art, each view (e.g., graphical representation/drawing) reveals information about the shape of the 3D object, showing a plurality of edges of the 3D object and any penetrations within the 3D object. Since each drawing view is 2D, the edges and the penetrations are typically depicted by lines and/or curves. Along with the lines and curves recorded on the view, is alphanumeric text relating to the actual physical dimension and edge of the 3D object, any penetration within the 3D object, and symbol property information regarding any symbol on the drawing. The alphanumeric text which is recorded on the document is frequently written, typed or printed on the document. The alphanumeric text provides information relating to the heights, widths, depths (lengths), radius of curvature (if the line is curved), as well as, directions and locations of these lines and curves. Sometimes, the direction of the line is implicit from the drawing view, as when a pair of adjacent lines are orthogonal to or collinear with each other (e.g. at 90.degree., 180.degree. or 270.degree. to each other).
Symbols may also be present on the view. The symbols include, but are not limited to, symbols for placement of moieties within the 3D object e.g., windows, doors, toilets, electrical outlets, or other features, or symbols for the sizes and shapes of apertures which may fully or partially penetrate the 3D object, or symbols which are indicia of certain shapes of cuts or surface features of the 3D object.
A vexatious problem, largely unattended in the art, is the lack of an accurate easy, quick and cost effective conversion of these hand drawn hard copy source documents depicting 3D objects into computer based drawings which are mathematically accurate and based on the recorded alphanumeric text present on the hard copy source document. Conversion is the process of taking a analog hard copy source document and changing it into a digital format suitable for use in a digital computer environment.
Some prior art has attempted to respond to some of the problems of converting this paper based information into a usable, reliable computer file. Unfortunately current methods are too slow, too inaccurate, too costly (because of labor intensiveness) or useful only for two dimensional representations. The prior art methods can be grouped into two major categories: manual entry and automated methods.
Manual entry of drawing information into a CAD program is slow and labor intensive and requires the user to read the alphanumeric text and symbols from sometimes a large unwieldy paper drawing and enter it into the computer. The user must constantly go back and forth between paper document and computer. This slow process is subject to possible error and delay. The advantages of the manual entry method are accuracy, when done correctly, and avoiding the costs of the hardware and software required by automated methods. Because it is labor intensive, it is not well suited for performing large volumes of conversions.
A number of automated methods are known in the art of conversion of cartographic documents (describing two dimensional (2D) land areas surveyed) for inputting hard copy document survey data into a computer file, manipulating the data using known coordinate geometry (COGO) software and CAD software packages to produce vectorized computer drawings. The most popular methods fall into two categories: the "manual digitizing method," and the "scanning method used with a vectorization of the graphics." [See, P. J. Stevenson, Scanning for Automated Data Conversion of Cartographic Documents, 1994, titled "Report No. 426 Department of Geodetic Science and Surveying, The Ohio State University, Columbus, Ohio/Report No. CFM-R-94-101, The Ohio State University Center for Mapping Columbus, Ohio", pp. 1-95, the disclosure of which is incorporated herein by reference; G. Omura, Mastering AUTOCAD B for DOS, SYBEX, Alameda, Calif. 1995, pp. 452-480]. The scanning method used with a vectorization of the graphics typically uses heads-up digitizing, line following and automated raster vectorization for converting scanned raster files to vector files. Major problems with using these methods include inaccurate drawing of the area surveyed on the hard copy document, scaling errors, typographical errors in keying typing in text, and scanner distortion of the information on the face of the hard copy document. Both the aforementioned manual digitizing method and automated methods for use with cartographic documents are described in detail along with the limitations of each method, in U.S. patent application Ser. No. 08/445,687 filed May 22, 1995, page 3, line 20 through page 5, line 27, the disclosure of which is incorporated herein by reference.
Also known in the art is an apparatus and method for manipulating scanned documents in CAD. [see, e.g. U.S. Pat. No. 5,353,393 to Bennett et al.] CAD generated images are overlaid over scanned raster images. The 2D CAD image is generated by tracing over the raster image or by using standard CAD commands. This is basically a 2D technique, since 3D CAD drawing packages were unknown at that time. The creation of the resultant 2D CAD drawing view has potential inaccuracy due to using a scaled raster drawing (which itself may be inaccurately drawn or may suffer from scanner distortion) or the data may be typed in incorrectly by the user in response to the CAD queries, or may be misread by the user of the CAD program.
Also optical character recognition has been most effective when recognizing text that is perfectly horizontal and of a standard font type. Recently, non-standard fonts and hand written text are recognized by the OCR. In a typical drawing or map to be converted, the alphanumeric text of concern is often written along the same angle as the line to which it refers. Techniques for recognizing hand drawn graphic symbols on scanned engineering drawings to produce vectorized graphic data, are known in the art. [See, Bhaskaran (U.S. Pat. No. 4,949,388).] Likewise, methods of processing information from scanned hard copy documents containing text or text and graphics and use of OCR recognized text is known. (Lech et al., U.S. Pat. No. 5,258,855). However this recognition process ignores the meaning behind the symbols and the text. It simply replaces the raster entity with either a vector representation or an ASCII based text string.
The same limitation exists with Optical Symbol Recognition (OSR). OSR works by comparing raster images of symbols with a pre-established library of symbols. The OSR recognizes the raster symbol and converts the raster symbol into a vector version of the same symbol and then places the vector version of the symbol in approximately the same location on the raster drawing image as the raster image of the symbol. The user is still left to relate a symbol property to the symbol. By "symbol property" or "symbol property information" are meant hereinthroughout a physical dimension(s) and shape of a moiety that the symbol represents. The user must locate the symbol property and manipulate the drawing to incorporate this information into the drawing.
Recently a computer automated system and method for converting source documents bearing alphanumeric text relating to the length and directions of the bounding lines of an area surveyed using OCR recognition of the alphanumeric text has been discovered.(WO 96/37861). The alphanumeric text relating to the length and direction of the bounding lines of a land area surveyed treats only a two dimensional (2D) representation, e.g. the bounding lines are treated as in the same XY plane.
Engineering drawings and architectural plans are significantly different from the bounding lines of a land area surveyed because the lines (and/or curves) designating the edges of a surface of the 3D object are not necessarily in the same plane, although on the drawing (or plan) which is a 2D representation of the 3D object, they may appear to be so. The aforementioned inaccuracies of automated methods are particularly critical in a three dimensional environment because various edges of the surface of the 3D object must fit together exactly. Therefore, conventional automated conversion strategies are, at best, only capable of producing two dimensional results.
Also engineering drawings and architectural plans further differ from land survey maps in that the former have symbols thereon which are also associated with physical three dimensional symbol properties related to the moiety the symbol represents and to the placement of the moiety in the 3D object. The symbols may also have associated alphanumeric text providing the physical dimensions of the symbol property.
Despite recognition and study of various aspects of hard copy source document conversion to digital format, the prior art has produced very little in the way of providing an accurate computer automated system and method of converting a raster file of a scanned hard copy source document bearing a drawing view, symbols and alphanumeric text relating to the physical dimensions and edges of the 3D object being rendered, as well as the symbol associated with the 3D object, into mathematically accurate 3D vectors of the 3D object and of moiety the symbol represents and into a mathematically accurate vector computer drawing file based on the drawing, the symbol and alphanumeric text which was scanned from the source document.